FIELD OF THE INVENTION
[0001] The present invention relates to a transport frame control method and apparatus for
transmitting data units via a dedicated channel between a base station subsystem and
a radio network controller of a mobile communication system, such as a WCDMA (Wideband
Code Division Multiple Access) system for the UMTS (Universal Mobile Telecommunications
System).
BACKGROUND OF THE INVENTION
[0002] Third generation mobile telecommunications systems aim at providing end-users, apart
from terminal and personal mobility, with enhanced services. Compared to second generation
systems, enhancements that will cover features all the way between the end-user and
the core network elements are required, i. e. from mobile terminals to radio access
and fixed networks. The UMTS is such a third generation system, wherein, for example,
Asynchronous Transfer Mode (ATM) technologies may be selected so as to represent a
business environment and support fixed ATM terminals.
[0003] Delivering wide band multimedia services will require additional performance compared
with today's wireless standards. In this respect, research has been conducted focusing
on WCDMA which fully supports both packet- and circuit-switched communications such
as Internet browsing and land line telephone services, respectively.
[0004] WCDMA is based on a modern, layered network-protocol structure similar to the protocol
structure used in, for instance, GSM networks. This will facilitate the development
of new wireless wide band multimedia applications. With increasing demand for next-generation
mobile telephone services, there will be a new set of requirements on a wireless systems,
such as:
- support for high speed data communication;
- support for both packet- and circuit-switched services, such as internet traffic and
video conferencing;
- higher network capacity, better usage of the frequency spectrum, each user will require
more capacity compared to today's voice services;
- support for several connections.
[0005] Users will, for instance, be able to browse the Internet in parallel to voice calls
and/or video conferencing.
[0006] Recently, the European Telecommunications Standards Institute (ETSI) decided on WCDMA
as the radio technology for the paired bands of the UMTS. The same applies to the
standardization bodies of Japan and the USA. Consequently, WCDMA is the common radio
technology standard for third-generation wide-area mobile communications in Europe,
North America and Asia.
[0007] The WCDMA concept is based on a totally new channel structure for all layers (L1
to L3) built on technologies such as packet-data channels and service multiplexing.
The new concept also includes pilot symbols and a time-slotted structure. The paper
"UMTS/IMT-2000 based on Wideband CDMA" by Erik Dahlman, Björn Gudmundson, Mats Nilsson
and Johan Sköld, is concerned with the description of the W-CDMA air interface.
[0008] In practice, certain key parameters in WCDMA and GSM have been harmonized in order
to achieve an optimum solution for dual-mode GSM/UMTS terminals as well as GSM/UMTS
hand-over. This will facilitate today's users easy access to third-generation services
through dual-mode terminals, as will be the case with UMTS/GSM terminals.
[0009] In WCDMA systems, user plane data entities (in the following referred to as transport
blocks TB) need to be transported between a radio network controller (RNC) and a base
station (BS) of a mobile network like the GSM network. A frame layer control protocol
exists that handles the transmission between the above two network elements (BS and
RNC), which is referred to as Radio Block Transport Protocol (RBTP) in the following.
[0010] The RBTP is adapted to attach to a transport block TB all information which the layers
2/3 in the RNC and the layer 1 in the BS need to exchange. This information is necessary
for synchronization (e.g. a frame number to synchronize the transmission), outer loop
PC (e.g. a frame reliability information and a power control command), macro diversity
combining (e.g. a system frame number and the L1 cyclic redundancy check), indication
of L1 processing to be done (e.g. a transport format indicator TFI), and identification
of a channel to which the present TB belongs.
[0011] According to a known solution, a fixed structure of the RBTP frame for one kind of
channel is used, e.g. there is one structure for a dedicated channel with a fixed
number of bit reserved for every field.
[0012] However, the parameters necessary to be attached to the TB are different for different
kind of transport channels that the WCDMA system supports (e.g. common channels, dedicated
channel with and without soft handover possibility, high and low bit rate, fixed or
variable bit rate, best effort packet data channels), because the nature of the channels
and the characteristic of the data transmitted over them are different.
[0013] Therefore, the above known solution leads to the drawback that the transmission link
is not efficiently used, since the RBTP frame may contain information which is not
necessary or which can be specified with a minor number of bits, due to the specific
characteristic of the channel.
SUMMARY OF THE INVENTION
[0014] It is therefore an object of the present invention to provide a transport frame control
method and apparatus which allow flexibility and minimum usage of the transmission
link capacity.
[0015] This object is achieved by a transport frame control method according to claim 1.
[0016] Additionally, this object is achieved by a transport frame control apparatus according
to claim 8.
[0017] Accordingly, an adaptive frame type coding is provided, which allows a very efficient
usage of the transmission resources between the network elements, whereby the overhead
of the control information for the transmission of the user data is reduced to a minimum.
Moreover, the memory required to buffer the user data in the network elements is reduced.
This benefit is of particular advantage in WCDMA systems, because dedicated channels
with a wide range of characteristics are provided therein, and the usage of a common
structure for the transport leads to a high protocol overhead, particularly for speech
channels. Nevertheless, the above solution can be used in any communication system
having different types of connections.
[0018] In view of the fact that a minimum control information is used, processing capacity
can be reduced, since the decoding processing requires less processing capacity.
[0019] The frame type coding defines specific control information fields of the transport
frame and their bit number. Thus, unnecessary control information fields which are
not required for specific connection types of a dedicated channel can be canceled
or at least their bit number can be reduced, so as to reduce the overhead of the control
information. In particular, the bit number of a transport format indicator field can
be determined on the basis of the number of different transport format indicators
allowed for a dedicated channel.
[0020] Furthermore, the value of the transport format indicator field may define if and
how a whole original data unit is split into different data units to be transported
via the dedicated channel. Thereby, a segmentation of a transport data block may be
performed, if its dimension exceeds the maximum dimension allowed by the underlying
transport mechanism of the connection type of the dedicated channel.
[0021] Moreover, the value of the transport format indicator field may define the presence
and/or bit number of another one of said specific control information fields. Thereby,
a specific control information relating to the transport format of the connection
can be added or adapted. Such a specific control information may be a frame reliability
information required for high bit rate transmissions in order to improve quality control.
[0022] The coding format may be selected in a set-up phase of the dedicated channel based
on corresponding set-up parameters of the dedicated channel. Thus, the structure of
the transport frame readily can be changed when a change of the channel parameters
of the dedicated channel has been detected.
[0023] In case only one transport connection is allocated to the dedicated channel, a channel
indicator field may be deleted from the control information, since the network elements
at the receiving and the transmitting end already know the type of connection, such
that the frame type can be decoded at the receiving end using both the information
concerning the connection type and the short frame information code provided in a
transport frame itself.
[0024] The frame control method preferably may be used in a user plane interface of a WCDMA
system. The dedicated channel may be an ATM AAL2 channel, wherein the data unit may
be a user plane data unit.
[0025] In case the frame control method is used in a mobile communication system, such as
the GSM system, the network elements may comprise a base station and a radio network
controller.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] In the following the present invention will be described in greater detail on the
bases of a preferred embodiment with reference to the accompanying drawings in which:
Fig. 1 shows a block diagram of a mobile communication system connected to different
network types in order to deliver multimedia services,
Fig. 2 shows a principle diagram of a transport frame used in the frame control method
according to the present invention, and
Fig. 3 shows a principle block diagram of a network element comprising a frame control
apparatus according to the preferred embodiment of the invention.
[0027] The following preferred embodiment relates to a transport frame control method used
in a WCDMA system used in a mobile communication system.
[0028] According to Fig. 1, a mobile communication system 6 comprises a mobile station (MS)
1 radio-connected to a base station subsystem (BSS) 2. The BSS 2 is connected to a
radio network controller (RNC) 3 which may be connected to a circuit-switched network
like a Public Switched Telephone Network (PSTN) 4 and to a packet-switched network
like the Internet 5.
[0029] The WCDMA system enables a full support of both packet- and circuit-switched communications.
[0030] In the WCDMA system according to the preferred embodiment, the RBTP is used to adapt
the UMTS user plane interfaces Iur and Iub between the RNC 3 and the BSS 2. In particular,
the RBTP is used to adapt the TB, i.e. a user plane data unit such as a MAC PDU (Media
Access Control Packet Data Unit), to an AAL 2 channel (ATM Adaptation Layer type 2).
In such a transmission, the type of the transport frame (RBTP frame) has to be indicated
in each frame. However, in at least most connection types only a small subset of the
possible FCL frame types is used. The TBs (MAC PDUs) are encapsulated by the RBTP
in frames that contain all the relevant information which is to be exchanged between
the BSS 2 and the RNC 3.
[0031] Fig. 2 shows an example for such a transport frame. According to Fig. 2, the transport
frame consists of transport blocks TB and a control information portion CI comprising
a plurality of control information fields. The control information portion CI forms
the head of the transport frame and is may be called "header" of the transport frame.
The control information field CI is followed by a plurality of transport blocks TB
which correspond to the user plane data units (PDUs).
[0032] As indicated by the arrow in Fig. 2, the RBTP defines a connection type specific
frame type coding of the transport frame, wherein different bit rates and different
natures of the dedicated transport channel (e.g. an AAL 2 link) are considered. In
particular, the information fields of the control information portion CI of the transport
frame and their bit numbers are selected in accordance with the connection type of
the dedicated transport channel.
[0033] Fig. 3 shows a principle diagram of a downlink or uplink part of a network element
10 such as the RNC 3 or a base station controller BSC of the BSS 2, respectively.
The network element 10 is arranged at one end of a transmission link such as the AAL2
connection. An input signal comprising TBs to be transmitted via the AAL2 connection
is received by a receiving means 11 which extracts the TBs from the received input
signal and supplies the extracted TBs to a frame generating means 12. The frame generating
means 12 encapsulates the supplied TBs in frames in accordance with the RBTP, so as
to generate the RBTP frames to transmitted via the AAL2 connection.
[0034] Furthermore, a selecting means 13 is provided which receives from the receiving means
11 an information concerning the connection type of the dedicated transport channel.
This connection type information may be derived from received parameters of the dedicated
transport channel. Based on the connection type information, the selecting means 13
selects a specific frame type coding and controls the frame generating means 12 so
as to generate the RBTP frames in accordance with the selected frame type coding.
[0035] The frame type coding can be selected in the set-up phase based on the parameters
of the dedicated transport channel, and may be modified by the selecting means 13
when the parameters are changed. Moreover, in case different transport formats are
used in the dedicated channel, the transport format currently used for a specific
user plane data unit set may also specify if and how the whole user plane data unit
set is split into different TBs of the RBTP. Optionally, the value of a transport
format indicator (TFI) of the control information portion CI may also be used to determine
the presence and bit number of other information fields in the control information
portion and their bit numbers.
[0036] Thus, the frame type coding of the transport frame and particularly the length of
the control information portion CI depends on the connection characteristic of the
dedicated channel, in which they are used.
[0037] For example, the length in bit of a transport format indicator (TFI) field is given
by the number of the different TFIs that are allowed for that channel. Moreover, as
already said, the current TFI may define how a complete set of data units or transport
blocks (i.e. the transport block set which is processed as a single entity by the
OSI layer 1 of the BSS 2) is segmented (if necessary) into different transport frames.
The segmentation of the TB may be required if its dimension exceeds the maximum dimension
allowed by the underlying transport mechanism of the connecting type of the dedicated
channel.
[0038] An additional frame reliability information field may be provided in the control
information portion, if the TFI value indicates a high bit rate transmission via an
established connection. Thereby, quality control of the high bit rate transmission
can be improved. However, in case the TFI value indicates a low bit rate transmission
via the same connection, such a frame reliability information field is not provided
in the control information portion.
[0039] In the following, examples for different dedicated channels and their corresponding
frame type codings selected by the selecting means 13 are described:
[0040] A first dedicated channel DCH1 may be a speech channel with two transport formats
relating to 4.8 kbit/s and 0 kbit/s (Discontinuous Transmission, DTX). In this case,
each transport frame carries two transport blocks TB, transmitted in 20 ms, or no
data (speechless period), and may be composed such that the TBs are provided with
their Cyclic Redundancy Check (CRC) information or another reliability information.
The control information portion CI comprises a frame number (N bits, constant as a
system parameter), a TFI field of only one bit defining the two transport formats,
i.e. speech or no speech, and all relevant outer loop PC information.
[0041] Furthermore, a second dedicated channel DCH2 may be provided, to which a CS variable
rate connection with 16 different transport formats corresponding up to 256 kbit/s
is allocated. Here, the structure of the transport frame corresponds to that of the
DCH1, wherein the TFI field is composed of 4 bits the value of which determines how
the whole transport block set is segmented. For example, TFI = 16 indicates three
transport frames for every transport block set, wherein the structure of the second
and third frame is different from the structure of the first frame. In this case,
it is not necessary to specify any frame number in the second and third frame.
[0042] Additionally, a third dedicated channel BCH3 may be provided for a unidirectional
best effort packet data connection without macro diversity. In this case, the transport
frame not necessarily requires all the fields related to the outer loop PC and a macrodiversity
combiner in the control information portion CI. However, if a common pipe is used
to transport multiple dedicated channels of this type, the control information portion
CI of the transport frame must include a channel identifier.
[0043] As can be gathered from the above description of the preferred embodiment, the frame
type coding of the transport frame, i.e. fields and bit number per field of the control
information portion CI, its dimension and segmentation, is defined for each connection
type of the dedicated channel, and may change when the channel parameters defining
the connection type are changed. Thus, this connection type specific frame type coding
requires less bits then the above mentioned traditional coding method, and transmission
and processing capacity can be saved.
[0044] It should be understood that the above description and accompanying drawings are
only intending to illustrate the present invention. Thus, the transport frame control
method and apparatus according to the present invention may also be used in other
communications systems having different types of connections. The preferred embodiment
of the invention may vary within the scope of the attached claims.
[0045] A transport frame control method and apparatus is described for controlling a transport
frame used for transmitting a data unit via a dedicated channel between network elements
of a communication system having different types of connections.
[0046] The frame type coding of the transport frame is selected in accordance with a connection
type of the dedicated channel, such that a connection type specific frame length,
dimension and/or segmentation is achieved. This allows an efficient usage of transmission
resources, wherein an overhead of control information for the transmission of the
data units is minimized.
1. A transport frame control method for transmitting data units (TB) via a dedicated
channel between a base station subsystem (2) and a radio network controller (3) of
a mobile communication system (6), the transport frame control method comprising the
steps of:
(a) receiving parameters and deriving connection characteristics for the transmission
from the received parameters,
(b) selecting a transport frame type in accordance with the connection characteristics,
(c) receiving data units to be transmitted via the dedicated channel, and
(d) encapsulating said data units (TB) into transport frames according to the selected
frame type;
wherein a plurality of said transport frame types each comprise a plurality of formats
for transport frames including specific control information fields of the transport
frame and their number of bits,
wherein said specific control information fields include a transport format indicator
field, the value of which indicates which of said plurality of formats the transport
frame has, the number of bits of said transport format indicator field varying among
the plurality of transport frame types, and
wherein the value of said transport format indicator field also defines if and how
a whole original data unit set is split into different data units to be transported
via said dedicated channel.
2. A frame control method according to claim 1, wherein the value of said transport format
indicator field defines the presence and/or number of bits of another one of said
specific control information fields.
3. A frame control method according to claim 2, wherein said other one of said specific
control information fields is a frame reliability information field which is provided
when the value of said transport format indicator field indicates a high bit rate
transmission.
4. A frame control method according to any one of the preceding claims, wherein said
frame type coding is selected in a set-up phase of said dedicated channel based on
corresponding set-up parameters of said dedicated channel.
5. A frame control method according to claim 1, wherein said frame type coding does not
include a channel indicator field, if one transport connection is allocated to said
dedicated channel.
6. A frame control method according to any one of the preceding claims, wherein said
frame control method is used in a user plane interface of a WCDMA system.
7. A frame control method according to claim 6, wherein said dedicated channel is an
AAL 2 channel and said data unit is a user plane data unit.
8. A transport frame control apparatus for transmitting data units (TB) via a dedicated
channel between a base station subsystem (2) and a radio network controller (3) of
a mobile communication system (6), the transport frame control apparatus comprising:
(a) receiving means (11) configured to receive parameters and derive connection characteristics
for the transmission from the received parameters,
(b) selecting means (13) configured to select a transport frame type in accordance
with the connection characteristics,
(c) receiving means (11) configured to receive data units to be transmitted via the
dedicated channel, and
(d) frame generating means (12) configured to encapsulate said data units (TB) into
transport frames according to the selected frame type;
wherein a plurality of said transport frame types each comprise a plurality of formats
for transport frames including specific control information fields of the transport
frame and their number of bits,
wherein said specific control information fields include a transport format indicator
field, the value of which indicates which of said plurality of formats the transport
frame has, the number of bits of said transport format indicator field varying among
the plurality of transport frame types, and
wherein the value of said transport format indicator field also defines if and how
a whole original data unit set is split into different data units to be transported
via said dedicated channel.
1. Transportrahmensteuerverfahren zum Übertragen von Dateneinheiten (TB) über einen dedizierten
Kanal zwischen einem Basisstation-Subsystem (2) und einer Funknetzsteuerung (3) eines
Mobilkommunikationssystems (6), wobei das Transportrahmensteuerverfahren die folgenden
Schritte aufweist:
a) Empfangen von Parametern und Ableiten von Verbindungseigenschaften für die Übertragung
von den empfangenen Parametern,
b) Auswählen eines Transportrahmentyps gemäß den Verbindungseigenschaften,
c) Empfangen von über den dedizierten Kanal zu übertragenden Dateneinheiten, und
d) Einkapseln der Dateneinheiten (TB) in Transportrahmen gemäß dem ausgewählten Rahmentyp;
wobei aus einer Vielzahl der Transportrahmentypen jeder eine Vielzahl von Formaten
für Transportrahmen einschließlich spezifischer Steuerinformationsfelder des Transportrahmens
und ihrer Anzahl von Bits umfasst,
wobei die spezifischen Steuerinformationsfelder ein Transportformatindikatorfeld umfassen,
dessen Wert anzeigt, welche der Vielzahl von Formaten der Transportrahmen aufweist,
wobei die Anzahl von Bits des Transportformatindikatorfelds unter der Vielzahl von
Transportrahmentypen variiert, und
wobei der Wert des Transportformatindikatorfelds auch definiert, ob und wie ein ganzer
Originaldateneinheitssatz in unterschiedliche über den dedizierten Kanal zu transportierende
Dateneinheiten geteilt wird.
2. Rahmensteuerverfahren nach Anspruch 1, wobei der Wert des Transportformatindikatorfelds
die Präsenz und/oder Anzahl von Bits von einem anderen der spezifischen Steuerinformationsfelder
definiert.
3. Rahmensteuerverfahren nach Anspruch 2, wobei das andere der spezifischen Steuerinformationsfelder
ein Rahmenzuverlässigkeitsinformationsfeld ist, welches bereitgestellt wird, wenn
der Wert des Transportformatindikatorfelds eine hohe Bitratenübertragung anzeigt.
4. Rahmensteuerverfahren nach einem der vorstehenden Ansprüche, wobei die Rahmentypcodierung
in einer Setup-Phase des dedizierten Kanals basierend auf entsprechenden Setup-Parametern
des dedizierten Kanals ausgewählt wird.
5. Rahmensteuerverfahren nach Anspruch 1, wobei die Rahmentypcodierung kein Kanalindikatorfeld
umfasst, wenn eine Transportverbindung dem dedizierten Kanal zugewiesen wird.
6. Rahmensteuerverfahren nach einem der vorstehenden Ansprüche, wobei das Rahmensteuerverfahren
in einer Nutzerebeneschnittstelle eines WCDMA-Systems verwendet wird.
7. Rahmensteuerverfahren nach Anspruch 6, wobei der dedizierte Kanal ein "AAL 2"-Kanal
ist und die Dateneinheit eine Nutzerebene-Dateneinheit ist.
8. Transportrahmensteuervorrichtung zur Übertragung von Dateneinheiten (TB) über einen
dedizierten Kanal zwischen einem Basisstation-Subsystem (2) und einer Funknetzsteuerung
(3) eines Mobilkommunikationssystems (6), wobei die Transportrahmensteuervorrichtung
Folgendes aufweist:
a) eine Empfangseinrichtung (11), die eingerichtet ist, um Parameter zu empfangen
und Verbindungseigenschaften für die Übertragung von den empfangenen Parametern abzuleiten,
b) eine Auswahleinrichtung (13), die eingerichtet ist, um einen Transportrahmentyp
gemäß der Verbindungseigenschaften auszuwählen,
c) eine Empfangseinrichtung (11), die eingerichtet ist, um über den dedizierten Kanal
zu übertragende Dateneinheiten zu empfangen, und
d) eine Rahmenerzeugungseinrichtung (12), die eingerichtet ist, um die Dateneinheiten
(TB) in Transportrahmen gemäß dem ausgewählten Rahmentyp einzukapseln;
wobei aus einer Vielzahl der Transportrahmentypen jeder eine Vielzahl von Formaten
für Transportrahmen einschließlich spezifischer Steuerinformationsfelder des Transportrahmens
und ihrer Anzahl von Bits umfasst,
wobei die spezifischen Steuerinformationsfelder ein Transportformatindikatorfeld umfassen,
dessen Wert anzeigt, welche der Vielzahl von Formaten der Transportrahmen aufweist,
wobei die Anzahl von Bits des Transportformatindikatorfelds unter der Vielzahl von
Transportrahmentypen variiert, und
wobei der Wert des Transportformatindikatorfelds auch definiert, ob und wie ein ganzer
Originaldateneinheitssatz in unterschiedliche über den dedizierten Kanal zu transportierende
Dateneinheiten geteilt wird.
1. Procédé de détermination de trame de transport pour transmettre des unités de données
(TB) par l'intermédiaire d'un canal dédié entre un sous-système de station de base
(2) et un contrôleur de réseau radio (3) d'un système de communications mobiles (6),
le procédé de détermination de trame de transport comprenant les étapes consistant
à :
(a) recevoir des paramètres et dériver des caractéristiques de connexion pour la transmission
à partir des paramètres reçus,
(b) sélectionner un type de trame de transport conformément aux caractéristiques de
connexion,
(c) recevoir des unités de données destinées à être transmises par l'intermédiaire
du canal dédié, et
(d) encapsuler lesdites unités de données (TB) dans des trames de transport selon
le type de trame sélectionné ;
dans lequel une pluralité desdits types de trame de transport comprennent chacun une
pluralité de formats pour des trames de transport comprenant des champs d'informations
de détermination spécifiques de la trame de transport et leur nombre de bits,
dans lequel lesdits champs d'informations de détermination spécifiques comprennent
un champ indicateur de format de transport, dont la valeur indique le format parmi
ladite pluralité de formats que la trame de transport possède, le nombre de bits dudit
champ indicateur de format de transport variant parmi la pluralité de types de trame
de transport, et
dans lequel la valeur dudit champ indicateur de format de transport définit également
si et la manière dont un jeu entier d'unités de données originales est divisé en unités
de données différentes destinées à être transportées par l'intermédiaire dudit canal
dédié.
2. Procédé de détermination de trame selon la revendication 1, dans lequel la valeur
dudit champ indicateur de format de transport définit la présence et/ou le nombre
de bits d'un autre desdits champs d'informations de détermination spécifiques.
3. Procédé de détermination de trame selon la revendication 2, dans lequel ledit autre
desdits champs d'informations de détermination spécifiques est un champ d'informations
de fiabilité de trame qui est fourni lorsque la valeur dudit champ indicateur de format
de transport indique une transmission à haut débit.
4. Procédé de détermination de trame selon une quelconque des revendications précédentes,
dans lequel un codage dudit type de trame est sélectionné dans une phase d'établissement
dudit canal dédié sur la base de paramètres d'établissement correspondants dudit canal
dédié.
5. Procédé de détermination de trame selon la revendication 1, dans lequel un codage
dudit type de trame ne comprend pas de champ indicateur de canal, si une connexion
de transport est attribuée audit canal dédié.
6. Procédé de détermination de trame selon une quelconque des revendications précédentes,
dans lequel ledit procédé de détermination de trame est utilisé dans une interface
de plan d'utilisateur d'un système WCDMA.
7. Procédé de détermination de trame selon la revendication 6, dans lequel ledit canal
dédié est un canal AAL 2 et ladite unité de données est une unité de données de plan
d'utilisateur.
8. Appareil de détermination de trame de transport pour transmettre des unités de données
(TB) par l'intermédiaire d'un canal dédié entre un sous-système de station de base
(2) et un contrôleur de réseau radio (3) d'un système de communications mobiles (6),
l'appareil de détermination de trame de transport comprenant :
(a) des moyens de réception (11) configurés pour recevoir des paramètres et dériver
des caractéristiques de connexion pour la transmission à partir des paramètres reçus,
(b) des moyens de sélection (13) configurés pour sélectionner un type de trame de
transport conformément aux caractéristiques de connexion,
(c) des moyens de réception (11) configurés pour recevoir des unités de données destinées
à être transmises par l'intermédiaire du canal dédié, et
(d) des moyens générateurs de trame (12) configurés pour encapsuler lesdites unités
de données (TB) dans des trames de transport selon le type de trame sélectionné ;
dans lequel une pluralité desdits types de trame de transport comprennent chacun une
pluralité de formats pour des trames de transport comprenant des champs d'informations
de détermination spécifiques de la trame de transport et leur nombre de bits,
dans lequel lesdits champs d'informations de détermination spécifiques comprennent
un champ indicateur de format de transport, dont la valeur indique le format parmi
ladite pluralité de formats que la trame de transport possède, le nombre de bits dudit
champ indicateur de format de transport variant parmi la pluralité de types de trame
de transport, et
dans lequel la valeur dudit champ indicateur de format de transport définit également
si et la manière dont un jeu entier d'unités de données originales est divisé en unités
de données différentes destinées à être transportées par l'intermédiaire dudit canal
dédié.